The present invention relates to integrated circuit manufacturing. More specifically, the present invention relates to a device for detecting whether an apparatus, such as one used in manufacturing and development environments, is grounded sufficiently.
Due to the sensitive nature of modern integrated circuits, care must be taken to ensure adequate grounding of equipment and work spaces used near these devices. Without adequate grounding, static electricity may build up and cause an electrostatic discharge (ESD) event. ESD events may cause damage to the integrated circuit. To prevent this static electricity build up, grounding cables are often provided to electrically couple apparatuses such as work benches, tables, people, tools, equipment, and other conductive objects to earth ground. These grounding cables provide a conductive path to earth ground so as to shunt any static electricity to earth ground before it can build up.
Problems may occur with the grounding cables in many manufacturing and design environments. The grounding cables may be accidentally or intentionally disconnected. With the grounding cable disconnected, the equipment is no longer adequately grounded. If the disconnected ground cable goes undetected, integrated circuits may become damaged by an ESD event. Consequently, disconnected grounding cables may have negative effects on quality control in a manufacturing environment.
A variety of monitoring devices are presently on the market which can detect whether a particular apparatus is properly grounded. However, presently available devices have limitations. For example, one such device operates from an AC power source and requires the user to manually perform a series of tests to verify the grounding integrity of the apparatus. Such a system requires the user to follow correct procedures to ensure a proper grounding. If the tests are not completed, the monitor does not indicate a fault in the grounding system. So, the monitor is only as good as the people executing the procedures. Furthermore, no indication is given of a grounding cable that becomes disconnected between the performance of the tests. Consequently, the integrated circuits may be damaged in the time between the disconnection of the cable and the subsequent performance of the test.
Additionally, the use of AC power can cause problems in manufacturing or design environments. For example an AC power source must be conveniently available, the power source may accidentally be unplugged, the power supply may fail, or electromagnetic interference may be generated which effects the monitoring circuit. If the power supply is disconnected so the monitor no longer operates properly, currently available devices do not give an indication that a problem exists. So the user may not detect grounding problems even after following the testing procedures.
Consequently, an improved device for monitoring the integrity of ground connection is desirable.